This invention relates to control means and particularly, though not exclusively, to control means for clutches. In particular, though again not exclusively, the invention is concerned with such control means for use in connection with vehicle transmissions which include clutches and in which a prime mover drives an auxiliary two speed gearing and a change speed gearbox arranged in series.
The invention is also concerned with clutch assemblies including such control means.
In one form of prime mover and auxiliary gearing assembly, hereinafter referred to as "an assembly of the type specified", a prime mover drives an output shaft via a planetary gearing having two selectively engageable ratios, the planetary gearing comprising a sun wheel which is permanently fixed against rotation and first and second rotatable elements comprising an annulus gear and a planet carrier which carries planet gears which mesh both with the sun and annulus gears, one of said elements being driven directly by the prime mover at prime mover speed without the interposition of a clutch or gearing, the assembly including first and second clutch members carried by the first and second elements respectively for rotation therewith, a third clutch member carried by the output shaft and actuating means operable selectively to displace the third clutch member axially of the output shaft to engage the third clutch member with the first or second clutch members or to hold the third member disengaged from both the first and second clutch members.
In an assembly of the type specified in the preceding paragraph there may be said to be two clutches, one constituted by the first and third clutch members and the other constituted by the second and third clutch members. Thus for one ratio of the planetary gearing the first and third clutch members are clutched together, for the other ratio of the planetary gearing the second and third clutch members are clutched together and to disengage the output shaft of the assembly from the prime mover, in order for example to change gear in an associated change speed gearbox on the output side of the planetary gearing, the actuating means holds the third clutch member disengaged from the first and second clutch members. In other words, the two clutches which are provided serve both to control the planetary gearing and to disengage the prime mover from any change speed gearbox which may follow the planetary gearing.
It is an object of the present invention to provide a control means which in one form may be used, amongst other things, as part of the actuating means of an assembly of the type specified.